In a large pot of boiling salted water, cook pasta according to package instructions; drain well.
Heat olive oil in a large stockpot or Dutch oven over medium heat. Add garlic and onion, and cook, stirring frequently, until onions have become translucent, about 2-3 minutes. Stir in chicken stock, crushed tomatoes, green chiles, chili powder, cumin, oregano and cayenne pepper; season with salt and pepper, to taste.
Reduce heat to low; simmer, covered, until thickened, about 15 minutes. Stir in pasta, chicken, corn, cilantro and lime juice until heated through, about 2 minutes.
Serve immediately, garnished with avocado and tortilla strips, if desired.